Apparatus for forming metal film

ABSTRACT

An apparatus for metal plating on a substrate with through-holes includes a chamber that the substrate is disposed inside the chamber to be divided into two sections. A pressure generator and a pressure controller are connected to this and correspond to two sides of the substrate respectively. The pressure generator is used for pumping a electrolyte flowed parallel to the surface of the substrate into the chamber. The pressure controller is used for channeling the electrolyte off the chamber and controlling the pressure differences between the two sides of the substrate. So that the electrolyte flowed parallel to the surface of the substrate is pumped by the pressure generator and it passes several through-holes to control the thickness of metal plating on the.substrate and inner walls of the through-holes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 094147334 filed in Taiwan, R.O.C. onDec. 29, 2005, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an apparatus for forming a metal film,in particular an apparatus for forming a metal film with a uniformthickness on the surface of a substrate and on the inner wall of athrough-hole in the substrate.

2. Related Art

With the development of electronic devices, printed circuit boards(PCBs) have been gradually developed for high density packaging, suchthat the line width of a metal circuit formed on a surface has becomesmaller, and the aperture of a through-hole in the surface for a pin ofan electronic element to pass through has been gradually reduced.Therefore, the thickness of the metal films formed on printed circuitboards must be highly uniform; and defects of the metal films must beminimized, so as to improve the ductility and tensile strength, andprevent printed circuit boards from being cracked and broken due tothinner circuits and insufficient strength.

Japanese Patent JP56-58999 provides an apparatus for washing a substrateon which a metal film is to be formed, while the substrate is conveyedbetween two tanks, such that the time consumed for washing the substrateis reduced. In US Patent U.S. Pat. No. 5,077,099, a periodic vibrationsource is provided for vibrating the substrate. The electrolyte isdriven by vibration on the surface of a substrate and is circulated. Themethod controls the thickness of a metal film uniformly. In US PatentU.S. Pat. No. 5,077,099, only the thickness of the metal film on thesurface of the substrate can be improved. But for the metal film on theinner wall of the through-holes in the substrate, the electrolyte cannotflow within the through-holes and even cannot wet the through-holeseffectively. Moreover, as the dimension of through-hole reduces, theaspect ratio, the proportion between the axial length and the radialwidth increases. So that forming metal film within the through-holesbecome more difficult. Also the metal films formed on the inner walls ofthe through-holes are extremely poor, and affect the yield of printedcircuit boards. Therefore, how to design a desirable metal filmtechnology directed to through-holes with small apertures and highaspect ratios has become an important issue.

SUMMARY OF THE INVENTION

In view of aforementioned problem, the object of the present inventionis to provide an apparatus for forming a metal film to solve the problemthat prior to when the metal film is formed on the substrate, thethickness of the metal films on the surface of a substrate and on innerwalls of through-holes is non-uniform.

In order to achieve the aforementioned object, an apparatus for forminga metal film is provided to form the metal film on the substrate with atleast one through-hole, and comprises a sealed chamber, a pressuregenerator, and a pressure controller. The substrate is disposed withinthe sealed chamber to divide the sealed chamber into a first section anda second section. The pressure generator and the pressure controller areconnected to the sealed chamber and correspond to the first and secondsections, respectively. The pressure generator is used to pump aelectrolyte and enable it to flow in parallel with the surface of thesubstrate, and the pressure controller is used to derive the electrolyteand control the pressure difference between the two sides of thesubstrate. Thereby, the electrolyte is pumped by the pressure generatorto flow into the sealed chamber, so as to flow in parallel with thesurface of the substrate and to flow through the through-holes.Therefore, through the adjustment of the pressure controller, thethickness of the metal films formed respectively on the surface of thesubstrate and on the inner walls of the through-holes is controlled.

According to another embodiment of the present invention, the apparatusfor forming a metal film further comprises an electrolyte stabilizingdevice for stirring the electrolyte flowing into the sealed chamber, soas to enable solute and solvent in the electrolyte to be fully mixed,such that the ingredients are more uniform.

According to another embodiment of the present invention, the apparatusfor forming a metal film further comprises a temperature controller forcontrolling the temperature of the electrolyte flowing into the sealedchamber, so as to control the conditions for forming the metal film.

According to another embodiment of the present invention, the apparatusfor forming a metal film further comprises a laminar flow stabilizingdevice for eliminating the boundary layer of the fluid flowing into thesealed chamber, such that the flow rate of the electrolyte on thesurface of the substrate will become more uniform.

According to another embodiment of the present invention, the apparatusfor forming a metal film further comprises a flow rate controllingelement disposed in the sealed chamber. Through adjusting the spacebetween the flow rate controlling element and the surface of thesubstrate, the flow rate of the fluid flowing on the surface of thesubstrate can be adjusted.

According to another embodiment of the present invention, the apparatusfor forming a metal film further comprises an electric field controllerwith two electrodes. Two electrodes are immersed in the electrolyte inthe sealed chamber and located on the two sides of the substrate, so asto generate an electric filed. Thus, the substrate is located in theelectric field to strengthen the metal film forming effect.

Further scope of applicability of the present invention. will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

Both the foregoing general description about the present invention andthe following detailed description about the embodiments are intended todemonstrate and explain the principles of the present invention, and toprovide further explanation of the present invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below for illustration only, and whichthus is not limitative of the present invention, and wherein:

FIG. 1 shows an apparatus for forming metal film according to thepresent invention;

FIG. 2 is an exploded view of the apparatus for forming metal filmaccording to a first embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view depicted in FIG. 2;

FIG. 4 is a system block diagram depicted in FIG. 2;

FIG. 5 is a system block diagram of the apparatus for forming metal filmaccording to a second embodiment of the present invention;

FIGS. 6 and 7 are system block diagrams of other implementation aspectsaccording to the second embodiment of the present invention;

FIG. 8 is a system block diagram of the apparatus for forming metal filmaccording to a third embodiment of the present invention; and

FIG. 9 is a system block diagram of the apparatus for forming metal filmaccording to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In order to make the objects, structures, features, and functions of thepresent invention more comprehensible, preferred embodiments accompaniedwith figures are described in detail below.

Please refer to FIG. 1 of an apparatus for forming a metal filmaccording to the present invention. The apparatus for forming metal filmcomprises a frame 1, a delivery system 2, and a plurality of electrolytetanks A, B, C, D, E, F, G, H, and I. The delivery system 2 is disposedabove the frame 1 to move a substrate to be processed among each of theelectrolyte tanks A, B, C, D, E, F, G, H, and I. Each of the electrolytetanks A, B, C,.D, E, F, G, H, and I is used to conduct a surfacetreatment process and a metal film forming process, respectively. Thesurface treatment process is used to form a substrate film on thesurface of the substrate, and after that, a catalyst is coated on thesurface of the substrate in a specific pattern. Next, the metal filmforming process is conducted to deposit the metal on the region coatedwith the catalyst, so as to form the metal film with a predeterminedpattern. The apparatus for forming a metal film of the present inventioncan be applied in each of the electrolyte tanks to enable the platesolutions with different ingredients or the deionized water to flow onthe surface of the substrate uniformly, so as to control the grownthickness of the metal film.

FIGS. 2, 3, and 4 show the apparatus for forming a metal film accordingto the first embodiment of the present invention. The apparatus forforming a metal film can be applied to any of the aforementionedelectrolyte tanks. Each of the electrolyte tanks includes a sealedchamber 10, and the substrate 20 to be processed is disposed within thesealed chamber 10 and divides the sealed chamber 10 into a first sectionand a second section. Additionally, each substrate 20 is provided with aplurality of through-holes 21, such that the fluid may flow through thesubstrate 20 and circulate between two sides of the substrate 20.

A fluid feeding element 11 and a fluid deriving element 12 are furtherdisposed within the sealed chamber 10. The fluid feeding element 11 isshaped as a frame. Also, a circulating pipe 111 is disposed within thefluid feeding element 11 and connected to a pressure generatingapparatus 31 via a connecting tube, such that the electrolyte or thedeionized water is fed into the circulating pipe 111 and flows into thesealed chamber 10 via the apertures 112 formed at the inner edge of thefluid feeding element 11. The fluid deriving element 12 is substantiallythe same as the fluid feeding element 11, shaped as a frame. Also, acirculating pipe 121 is disposed within the fluid deriving element 12,and a plurality of apertures 122 is formed in the inner edge and usedfor absorbing the electrolyte in the sealed chamber 10, and thenderiving the electrolyte out of the sealed chamber 10 via a pressurecontroller 32 connected to the fluid deriving element 12. The fluidfeeding element 11 and the fluid deriving element 12 are disposed inparallel with the two sides of the substrate 20, such that the pressuregenerator 31 and the pressure controller 32 are correspondinglyconnected to the first and second sections of the sealed chamber 10,respectively.

The fluid feeding element 11 and the fluid deriving element 12 aredisposed at the two sides of the substrate 20 in parallel with eachother, such that the direction of the apertures 112 and 122 in the inneredge is parallel to the surface of the substrate 20. Therefore, both thefluid fed into the sealed chamber 10 through the fluid feeding elementland the fluid ,such as the electrolyte or the deionized water, drawnout by the fluid deriving element 12 flow in the direction parallel tothe surface of the substrate 20 and flow through the through-holes 21 inthe direction perpendicular to the substrate 20. The pressure generator31 can be a fluid pump, and the pressure controller 32 can be a valve.The pressure difference between the two sides of the substrate 20 iscontrolled through adjusting the pressure generator 31 together with thepressure controller 32, so as to adjust the flow rate. Thus, the flowrate 41 of the fluid flowing in parallel with the surface of thesubstrate 20 is the same as that of the flow rate 42 of the fluidflowing through the through-holes 21. As such, the conditions forforming the metal film on the surface of the substrate 20 are similar tothose for forming it on the inner walls of the through-holes 21, suchthat the growing rate of the metal film on the surface of the substrate20 is the same as that of the metal film on the inner walls of thethrough-holes 21. Therefore, the thickness of the metal film is uniformand the electrical conductivity or the stress is relatively uniform, andno significant difference occurs. A predetermined pattern is formed onthe surface of the substrate 20 via the catalyst. When the substrate 20is immersed in the electrolyte, an ion or a proton exchange occursbetween the ingredients of the electrolyte and the catalyst, such thatthe metal is precipitated and plated on the substrate to form a pattern.

Referring to FIG. 5, it shows the apparatus for forming a metal filmaccording to the second embodiment of the present invention. As shown inFIG. 5, an electrolyte stabilizing device 51 is further disposed betweenthe pressure generator 31 and the sealed chamber 10. The electrolytestabilizing device 51 is used to stir the electrolyte, such that thesolute and the solvent in the electrolyte are mixed more uniformly tofurther stabilize the quality of the electrolyte. For the embodiment,the electrolyte stabilizing device 51 is a stirring device, which stirsthe electrolyte before it flows into the sealed chamber 10, so as tofurther stabilize the feature of the electrolyte.

Referring to FIGS. 6 and 7, the electrolyte stabilizing device can be agas source 52, which feeds the gas into the electrolyte and stirs theelectrolyte by tiny bubbles. The gas is fed into the electrolyte beforeit flows into the sealed chamber 10 and stabilizes the electrolyte inadvance, as shown in FIG. 6. The gas source 52 also can be connected tothe fluid feeding element 31, and then the gas is directly fed into thesealed chamber 10 to stir and stabilize the electrolyte in the sealedchamber 10, as shown in FIG. 7.

Please refer to FIG. 8 of a system block diagram of the apparatus forforming a metal film according to the third embodiment of the presentinvention. In order to control the condition of the electrolyteeffectively, a temperature controller 53 and a laminar flow stabilizingdevice 54 are disposed between the pressure generator 31 and thepressure controller 32 in this embodiment, and the status of the fluidboundary layer of the electrolyte is changed before being fed into thesealed chamber 10 by the pressure generating apparatus 31, such that theflow rate of the electrolyte flowing in parallel with the surface of thesubstrate-20 is uniform and stable.

The temperature controller 53 includes a heater, used to control thetemperature of the electrolyte. Thus, an optimal reaction temperature isachieved before the electrolyte flows into the sealed chamber 10, so asto enhance the rate for forming the metal film. The laminar flowstabilizing device 54 is consisted of a porous medium. Since thethickness of the boundary layer of the fluid is gradually increased dueto the flowing of the electrolyte within the pipe, the flow rate of theelectrolyte is not uniform when the electrolyte reaches the substrate20. If the electrolyte flows through the laminar flow stabilizing device54 before flowing into the sealed chamber 10, the laminar flowphenomenon is destroyed, and the boundary layer grows once again. Thus;when the electrolyte flows into the sealed chamber 10, the flow ratebecomes more uniform, such that the growth rate and the thickness of themetal film will be relatively uniform.

Additionally, a flow rate controlling element 55 is further provided inthis embodiment, which is a plate body moving relative to the substrate20 to adjust the space W between the flow rate controlling element 55and the substrate 20, the flow rate of the electrolyte flowing on thesurface of the substrate 20 can be changed. Thus, the flow rate of theelectrolyte can be further adjusted.

Please refer to FIG. 9 of a schematic view of the apparatus for forminga metal film according to the fourth embodiment of the presentinvention. In order to further control the metal film forming processand strengthen the metal film forming rate, an electric field controller56 is disposed to generate an alternating current or a direct current.The electric field controller 56 has two electrodes 561 disposed withinthe sealed chamber 10, immersed in the electrolyte, and located on thetwo sides of the substrate 20 respectively. Through applying a directcurrent or an alternating current, the substrate 20 is disposed withinan electric field to strengthen the metal film forming rate.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded asdeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. An apparatus for forming a metal film on a substrate with at leastone through-hole, comprising: a sealed chamber, wherein the substrate isdisposed within said sealed chamber and divide said sealed chamber intoa first section and a second section; a pressure generator,correspondingly connected to the first section of said sealed chamber,for pumping electrolyte to flow in parallel with the surface of thesubstrate; and a pressure controller, correspondingly connected to thesecond section of said sealed chamber, for deriving the electrolyte andcontrolling the pressure difference between two sides of the substrate;wherein the electrolyte is pumped by said pressure generator into saidsealed chamber, flowing in the direction parallel to the surface of thesubstrate and flowing through the through-holes in the directionperpendicular to the substrate, and the thickness of the metal filmgrown in parallel with the surfaces of the substrate and thethrough-hole are uniformly formed.
 2. The apparatus for forming a metalfilm as claimed in claim 1, further comprising a electrolyte stabilizingdevice disposed between the substrate and said pressure generator, forstirring the electrolyte and stabilizing the quality of the electrolyte.3. The apparatus for forming a metal film as claimed in claim 2, whereinsaid electrolyte stabilizing device is a gas source for feeding a gas,so as to stir the electrolyte.
 4. The apparatus for forming a metal filmas claimed in claim 2, wherein said electrolyte stabilizing device is astirring device.
 5. The apparatus for forming a metal film as claimed inclaim 1, further comprising a laminar flow stabilizing device disposedbetween said pressure generator and said sealed chamber, for changingthe state of the fluid boundary layer of the electrolyte, such that theflow rate of the electrolyte flowing in parallel with the substrate isuniform and stable.
 6. The apparatus for forming a metal film as claimedin claim 5, wherein said laminar flow stabilizing device is a porousmedium.
 7. The apparatus for forming a metal film as claimed in claim 1,further comprising an electric field controller with two electrodes,wherein the two electrodes are immersed in the electrolyte and disposedon the two sides of the substrate respectively, so as to generate anelectric field.
 8. The apparatus for forming a metal film as claimed inclaim 7, wherein a direct current is applied between the two electrodes.9. The apparatus for forming a metal film as claimed in claim 7, whereinan alternating current is applied between the two electrodes.
 10. Theapparatus for forming a metal film as claimed in claim 1, furthercomprising a temperature controller for controlling the temperature ofthe electrolyte.
 11. The apparatus for forming a metal film as claimedin claim 1, further comprising a flow rate controller disposed withinsaid sealed chamber, wherein said flow rate controller moves relative tothe substrate to adjust the space there-between, so as to control theflow rate of the electrolyte when flowing in parallel with the surfaceof the substrate.
 12. The apparatus for forming a metal film as claimedin claim 1, wherein said pressure generator is a liquid pump.
 13. Theapparatus for forming a metal film as claimed in claim 1, furthercomprising a fluid feeding element disposed within said sealed chamberand connected to said pressure generator, and located on one side of thesubstrate, for guiding the electrolyte to be flowed in parallel with thesurface of the substrate.
 14. The apparatus for forming a metal film asclaimed in claim 13, wherein said fluid feeding element is shaped as aframe, with a circulating pipe disposed therein, and with a plurality ofthrough holes located at an inner edge of the circulating pipe.
 15. Theapparatus for forming a metal film as claimed in claim 1, wherein thesubstrate has a pattern formed with a catalyst, when the substrate isimmersed in the electrolyte, an ion or a proton exchange is conductedbetween the electrolyte and the catalyst, forming the metal film withthe pattern.
 16. The apparatus for forming a metal film as claimed inclaim 1, further comprising a fluid deriving element disposed withinsaid sealed chamber and connected to said pressure generation device,and located on one side of the substrate, for guiding the electrolyte tobe flowed in parallel with the surface of the substrate.
 17. Theapparatus for forming a metal film as claimed in claim 16, wherein saidfluid deriving element is shaped as a frame, with a circulating pipedisposed therein, and with a plurality of through holes located at aninner edge of the circulating pipe.